SUMMARY Existing therapies for inflammatory bowel disease based on broad suppression of inflammation result in variable clinical benefit and unwanted side effects. A potential therapeutic approach for promoting immune tolerance is the in vivo induction of regulatory T cells (Tregs). Here we report that activation of the aryl hydrocarbon receptor using the non-toxic agonist 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) induces human Tregs in vitro that suppress effector T cells through a mechanism mediated by CD39 and Granzyme B. We then developed a humanized murine system whereby human CD4+ T cells drive colitis upon exposure to 2,4,6-trinitrobenzenesulfonic acid and assessed ITE as a potential therapeutic. ITE administration ameliorated colitis in humanized mice with increased CD39, Granzyme B, and IL-10-secreting human regulatory T cells. These results develop an experimental model to investigate human CD4+ T responses in vivo and identify the non-toxic AHR agonist ITE as a potential therapy for promoting immune tolerance in the intestine.

IL10 receptor (IL10R)-deficient mice develop spontaneous colitis and similarly, patients with loss-of-function mutations in IL10R develop severe infant-onset inflammatory bowel disease (IBD). Loss of IL10R signaling in mouse and human macrophages is associated with increased production of interleukin 1 beta (IL1B). We demonstrated that innate immune production of IL1B mediates colitis in IL10R-deficient mice. Transfer of Il1r1−/− CD4+ T cells into Rag1−/−/Il10rb−/− mice reduced the severity of their colitis (compared to mice that received CD4+ T cells that express IL1R), accompanied by decreased production of interferon gamma, tumor necrosis factor, and IL17A. In macrophages from mice without disruption of IL10R signaling or from healthy humans (controls), incubation with IL10 reduced canonical activation of the inflammasome and production of IL1B through transcriptional and post-translational regulation of NLRP3. Lipopolysaccharide (LPS) and adenosine triphosphate stimulation of macrophages from Il10rb−/− mice or IL10R-deficient patients increased production of IL1B. Moreover, in human IL10R-deficient macrophages, LPS stimulation alone increased IL1B secretion via non-canonical, caspase 8-dependent activation of the inflammasome. We treated 2 IL10-receptor deficient patients with severe and treatment-refractory infant-onset IBD with the IL1 receptor antagonist anakinra. Both patients had marked clinical, endoscopic, and histologic responses after 4–7 weeks. This treatment served as successful bridge to allogeneic hematopoietic stem cell transplantation in 1 patient. Our findings indicate that loss of IL10 signaling leads to intestinal inflammation, at least in part, through increased production of IL1 by innate immune cells, leading to activation of CD4+ T cells. Agents that block IL1 signaling might be used to treat patients with IBD resulting from IL10R deficiency.

Mutations in Wiskott–Aldrich syndrome protein (WASP) cause autoimmune sequelae including colitis. Yet, how WASP mediates mucosal homeostasis is not fully understood. Here we show that WASP-mediated regulation of anti-inflammatory macrophages is critical for mucosal homeostasis and immune tolerance. The generation and function of anti-inflammatory macrophages are defective in both human and mice in the absence of WASP. Expression of WASP specifically in macrophages, but not in dendritic cells, is critical for regulation of colitis development. Importantly, transfer of WT anti-inflammatory macrophages prevents the development of colitis. DOCK8-deficient macrophages phenocopy the altered macrophage properties associated with WASP deficiency. Mechanistically, we show that both WASP and DOCK8 regulates macrophage function by modulating IL-10-dependent STAT3 phosphorylation. Overall, our study indicates that anti-inflammatory macrophage function and mucosal immune tolerance require both WASP and DOCK8, and that IL-10 signalling modulates a WASP-DOCK8 complex.

BackgroundAlthough deleterious mutations in interleukin-10 and its receptor molecules cause severe infantile-onset inflammatory bowel disease, there are no reports of mutations affecting this signaling pathway in Japanese patients. Here we report a novel exonic mutation in the IL10RA gene that caused unique splicing aberrations in a Japanese patient with infantile-onset of inflammatory bowel disease in association with immune thrombocytopenic purpura and a transient clinical syndrome mimicking juvenile myelomonocytic leukemia.Case presentationA Japanese boy, who was the first child of non-consanguineous healthy parents, developed bloody diarrhea, perianal fistula, and folliculitis in early infancy and was diagnosed with inflammatory bowel disease. He also developed immune thrombocytopenic purpura and transient features mimicking juvenile myelomonocytic leukemia. The patient failed to respond to various treatments, including elemental diet, salazosulfapyridine, metronidazole, corticosteroid, infliximab, and adalimumab. We identified a novel mutation (c.537G > A, p.T179T) in exon 4 of the IL10RA gene causing unique splicing aberrations and resulting in lack of signaling through the interleukin-10 receptor. At 21 months of age, the patient underwent allogeneic hematopoietic stem cell transplantation and achieved clinical remission.ConclusionsWe describe a novel exonic mutation in the IL10RA gene resulting in infantile-onset inflammatory bowel disease. This mutation might also be involved in his early-onset hematologic disorders. Physicians should be familiar with the clinical phenotype of IL-10 signaling defects in order to enable prompt diagnosis at an early age and referral for allogeneic hematopoietic stem cell transplantation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12876-016-0424-5) contains supplementary material, which is available to authorized users.